1. Field of the Invention
This invention relates to attic ventilation fans, and more particularly concerns a turbine-type attic fan adapted to be secured from rotation and sealed from air passage during periods of cold weather.
2. Description of the Prior Art
Numerous attic ventilation devices have been disclosed in the prior art. Such devices typically are employed to exhaust hot air from the attic of a house or industrial structure during hot summer months. There are many varieties of attic ventilators. Some passive types of units are as simple as louvers or other vent means which merely allows the escape of heated air. Other units are thermostatically controlled and have electric fans or blowers designed to expel a greater airflow. These units often use as much energy as is saved by cooling the attic. Yet other ventilators utilize a rotating turbine fan which derives its rotational force from the wind acting upon a radial array of fan blades. Even a slight breeze is sufficient to create the required rotation for energy efficient attic cooling.
Various methods have been employed in attempts to selectively disable and enable such devices. For example, U.S. Pat. No. 4,924,760, to Jobson, discloses an attic ventilator fan having a vent damper device which is automatically closed in the event of a fire. A fusible link is employed to maintain the damper in an opened position until a predetermined threshold temperature is achieved. Once the elevated temperature created by a fire melts the fusible link, a spring pulls the damper to a closed position. Since the fusible link is a single use component, this damper is not easily opened and closed to allow for seasonal temperature changes.
Various other types of roof vent dampers have been disclosed in the prior art. A typical example of such roof vent damper is to be found in U.S. Pat. 2,183,645, issued to R. Hansen, which discloses a roof vent having a pivotal damper plate operable from a remote location through a rope and pulley mechanism. U.S. Pat. 2,218,926 to Telchmann concerns a damper system for an industrial building roof, and utilizes a pair of pivotal opposed dampers, U.S. Pat. 2,285,829 to A. Maage, Jr. discloses a damper regulator for a rectangular cross section ventilation duct, and is formed as a pivotally mounted rectangular plate. U.S. Pat. 2,923,225, issued to C. Massey discloses a roof ventilator having a pivotal damper plate which is biased to an open position by a counter weight and is manually closeable by a rope. U.S. Pat. 4,759,270, issued to Lindeen, discloses a vent cap cover for a recreational vehicle vent including a pivotal damper.
Although the aforementioned devices incorporate damping means for roof mounted ventilators, they are not specific to the turbine fan type ventilator. For example, the Massey damper is specifically applicable to a ventilator having an elongated rectangular cross section. The Jobson damper is not designed for interactive usage within a ventilator duct, and is mounted in a manner to occlude the roof aperture at the lower extremity of the duct. Such device is generically applicable to any ventilation duct or orifice.
Furthermore, the aforementioned devices are designed to block the majority of airflow through the vent by means of a damper device. However, due to the imperfect nature of the damper, a decreased airflow may still pass as a downdraft or convection current. A specific problem related to the turbine roof ventilator is that, although the airflow may be damped to some degree, the turbine unit continues to rotate with any significant breeze, thereby creating a draft across the damper device. A generally accepted practice has been to cover the turbine unit with a plastic sheet or other cover device. The wrapping of the fan serves several purposes. The draft is eliminated. Wear and tear caused by the normal turning of the fan is arrested during the period of non-usage, thereby lengthening the life of the fan. Moreover, potential damage to the fan blades by turning while encrusted with snow and ice is averted. However, the plastic or other wrapping material often will not withstand the wind, cold, and ultraviolet radiation of the sun. The cover usually tears free at times when inclement weather precludes climbing upon a rooftop to facilitate repair.
It is therefore an object of the present invention to provide a modified turbine fan attic ventilator device adapted to be secured from rotation during periods of non-use.
It is another object of the present invention to provide a device of the aforesaid nature which has damper means which may be closed during periods of non-use in order to prevent passage of draft currents.
It is a further object of this invention to provide a device of the aforesaid nature which is simple to operate, durable, and amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.